Many types of molds that grow both indoors and outdoors thrive in high humidity and low light. Molds often grow on the soil surfaces of indoor potted plants, because the soil usually stays damp from watering the plant and are out of direct sunlight. If you find mold growing on the soil of your houseplant, you may have mold growing in other places inside your home. Check for mold growth around your window frames, around pipes, in your basement, as well as on and beneath carpeting.
Spray the soil surface with an appropriate fungicide. Follow the directions carefully.
Move the houseplant closer to a window or in more direct, brighter sunlight. This will help to keep the soil surface drier and prevent mold growth.
Spread a 1- to 2-inch layer of pea gravel on the soil surface. The pea gravel will also help to prevent mold growth on the soil.
Cut back on watering the houseplant, especially during the winter. Water the plant no more than once every two weeks, as most plants don't require much water during their dormant season.